Francis Schaeffer in The Mark of the Christian:
We should never come to [differences] with true Christians without regret and without tears. Sounds simple, doesn’t it? Believe me, evangelicals often have not shown it. We rush in, being very, very pleased, it would seem at times, to find other men’s mistakes. We build ourselves up by tearing other men down. This can never show a real oneness among Christians.
There is only one kind of man who can fight the Lord’s battles in anywhere near a proper way, and that is the man who by nature is unbelligerent. A belligerent man tends to do it because he is belligerent; at least it looks that way. The world must observe that, when we must differ with each other as true Christians, we do it not because we love the smell of blood, the smell of the arena, the smell of the bullfight, but because we must for God’s sake. If there are tears when we must speak, then something beautiful can be observed.